Q15 - Salmonella is a food-borne microorganism

[tzyc]

I was not sure between (B) and (C)...and chose (C) thinking since it takes effect faster than the old one, it must be better.
Why is (B) correct instead?

Thank you for the help

[fmuirhea]

(C) talks about the treatment, not the test. Presumably, this faster new treatment would be applied regardless of the test used, so when comparing the old and new tests in terms of the treatment that follows them, it's a wash - it neither strengthens nor weakens.

This argument is based on a comparison, a common reasoning technique on the LSAT (and in real life). We have a bit of background about Salmonella: it's a food-borne microorganism, it can cause intestinal illness (that is itself sometimes fatal), etc. Then, we get to the meat of the comparison between conventional tests and the new test. There are some missing pieces, however - also quite common on the LSAT. Consider the breakdown below:

speed of test
conventional = slow
new = ?

identification strength
conventional = not great; can miss unusual strains
new = great; identifies by the one piece of genetic material common to all strains

So, the new test seems to be better than the old in terms of its ability to identify all strains of Salmonella - chalk up one point in the plus column. What's missing, however, is how long this test takes to return results. This information is particularly useful to making a determination of the test's effectiveness because the passage explicitly tells us that Salmonella can be fatal especially if not identified quickly and treated. If the test takes four months to return any results, it's really not a better option than the old test, notwithstanding its superior identification strength.

So, to strengthen the argument, chalk up another point in the plus column for the new test by confirming that it returns results quickly. In that case, the new test is ahead on the two factors discussed in the passage, so the conclusion that we should switch is made stronger.

Note that these two factors are not the only important factors to discuss when determining whether a switch should be made. The credited response to the following weaken question brings up another crucial dimension that has some bearing on our evaluation of the two tests: the level of Salmonella that will trigger a positive test.

(A) This tends to weaken, because perhaps some labs wouldn't be able to use the new test.
(C) Again, the treatment applies to both tests, so this is a positive for both options.
(D) Irrelevant - surely we still care enough about the few people who do get Salmonella to use the most effective test!
(E) We're interested not in remedies but in the testing procedure.

[ohthatpatrick]

Again, fmuirhea, I'm really impressed by the quality of your response!!

I can't think of anything I would possibly add/improve, except this:

We have a bit of background about Salmonella: it's a food-borne microorganism, it can cause intestinal illness (that is itself sometimes fatal), etc. Then, we get to the meat of the comparison [no pun intended] between conventional tests and the new test.